Apparatus for laying submerged pipe



Nov. 19, 1968 R. c. MosBY y 3,411,306

APPARATUS FOR LAYING SUBMERGED PIPE Filed July 7, 1965 5 Sheets-Sheet 21 INVENTOR. Ha/.Ld/ C'.` Mosby ATTORNEY @M2M/m R. C. MOSBY APPARATUS FORLAYING SUBMERGED PIPE 5 Sheets-Sheet 3 Filed July '2, 1965 ATTR/VEY Nov.I 19,1 1968 R. c. MosBY APPARATUS FOR LAYING SUBMERGBD PIPE Sheets-Sheet4 Filed July 7, 1965 vmm.

INVENTOR.

, ATTORNEY Nov'. 19, 1968 R. c. MosaY APPARATUS FOR LAYING SUBMERGEDPIPE 5 Sheets-Sheet 5 Filed July 7, 1965 R. www %y..\ ma .1|\\ WM# w w.C my x ma mw w 1 V m. NMWN QMKVQS United States Patent O 3,411,306APPARATUS FOR LAYING SUBMERGED PIPE Russell C. Mosby, Houston, Tex.,assignor to Zapata Oif- Shore Company, Houston, Tex., a corporation ofDelaware Filed July 7, 1965, Ser. No. 470,048 4 Claims. (Cl. 61'72.3)

ABSTRACTl OF THE DISCLOSURE A semisubmersible pipe laying bange has alongitudinally inclined ramp discharging at the lower front cornerthereof and a sealed portion in which the pipe can be joined and coatedbelow the water level.

This invention relates to apparatus for laying submerged pipe,particularly relatively large pipe of limited flexibility, in relativelydeep waters which may be subjected to heavy wind, wave, and/-or stormaction.

'Ihe usual procedure heretofore used in laying submerged pipe in deepwater has been to feed the made-up pipe string from the end of thelaying barge onto a ramp or other support means and thence to theunderlying Water bottom at such an angle that the pipe is notexcessively bent or otherwise s-trained in its suspended length betweenthe barge and the water bottom or due to change of direction of the pipeas it is laid on the bottom. These methods have become more and 4moreimpractical .as the diameter and, therefore, the stiffness of the pipebeing laid increases and also as the pertinent water depth increases.Furthermore, pipe support structures which project outwardly from thelaying barge are diflicult to disconnect from the pipe when it isnecessary to evacuate the scene because of an impending storm.

Accordingly, an object of the present invention is to provide novelapparatus for laying pipe such, for instance, as that used in gatheringfluids from oifshore oil and gas wells.

Another object is to provide improved means for laying very large apipeunder water for instance, pipe as large as 30 or 36 inches in diameter.

Another object is to provide means for laying submerged pipe wherein theangle of delivering of the pipe-laying structure does not becomeexcessive even though the depth of the water in which the pipe is beinglaid varies considerably.

Still another object is to provide pipe-laying apparatusAwhic'h can besafely left at the scene in case it iS necessary for the pipe-layingpersonnel to -be quickly removed from the scene.

Still another object is to provide novel pipe-laying apparatus which iswholly self-contained, which can be floated to its work area, eventhrough relatively shallow waters, land which can remain operative inrelatively deep and troubled waters.

According to the present invention, there is provided a rigid,skeletonized |hull structure .made up of elongated, hollow membersforming top and bottom hull portions and connecting vertical,longitudinal, and -other bracing elements where necessary. Extendingdiagonally through the structure is yan inclined, rigidly mounted pipeconveyor ramp on the upper portion of which pipe sections stored on theapparatus are connected to the pipe string on the ramy for periodicalemission from the bottom end of the ramp. The angle of the ramp isdesigned with respect to the water depth in which the apparatus isintended to operate and the submerged height of the apparatus so thatthe pipe is delivered from the apparatus at an angle which does notunduly strain the pipe being laid. Furthermore, ballast carried in thehollow framing members can be 3,411,306 Patented Nov. 19, 1968 ICCadjusted so as to maintain the bottom of the apparatus at substantiallya uniform -height above the water bottom which, accordingly, safelylimits the free, unsupported length' of the pipe. Finally, in case of animpending storm, it ispossible simply to sink the apparatus :and carrythe crew away in a workboat. When the storm has passed, the ballastpumps are operated to evacuate suicient of the ballast from the hollowframing members to raise the apparatus again to the desired height abovethe water bottom, whereupon pipe-laying operations can be promptlyresumed.

In the accompanying drawings which illustrate the invention,

FIG. l is a perspective view of lan exemplary embodiment of theinvention;

FIG. 2 is a ver-tical longitudinal central section through theapparatus;

FIG. 3 is -a plan view of the apparatus;

FIGS. 4 and 5 are transverse sections taken on the corresponding sectionlines of FIG. 3;

FIG. `6 is a horizontal section taken substantially on lines 6--6 ofFIG. 2 and showing the bottom hull structure;

FIG. 7 is a section taken substantially on line 7-7 of FIG. 2 andshowing the work, storage, and machinery areas; and

FIG. 8 is a diagram illustrating the manner of use of the apparatus.

The apparatus shown in the figures is intended for laying very large gasand/or oil gathering pipes in olfshore waters up to 240 feet or more indepth. The apparatus includes rigid framing forming a hull structureincluding a generally-horizontal bottom portion A, a top portion B, 1aninclined pipe conveyor ramp generally designated C, and deck stnictureD. Bottom hull structure A is formed of diverging, elongated, holowmembers 9 and 10 at the -rear end of the apparatus which merge withparallel front end members 11 and 12. The top hull structure consists ofsubstantially smaller tubular members 13 and 14 continued forwardly bytop sill members 15 and 16 upon which is supported the forward deckstructure D. Larger, hollow, vertical columns 17, 18, 19, and 20 andintervening smaller posts 21 connect the top and bottom hull structuresand transverse bracing members are provided at 22. Certain of the braces22 are disposed to underlie and support ramp C. The bottom hull isadditionally provided with diagonol bracing members 23 and the front endof the structure is provided with additional diagonal and verticalbraces 24 and 25.

The inclined pipe conveyor ramp 26, 27 has suitable rollers or otherelements, symbolized at 28 in FIG. 4, for facilitating sliding of thepipe string therealon-g. The ramp extends through a tubular housing 32of large diameter which extends diagonally from the lower rear end ofthe rigid, buoyant framing structure to the upper, forward end there-of,the extreme upper portion 27 of the ramp being mounted above deckstructure D upon an upstanding, triangular support 29. The lowerdelivery end 33 of housing 32 is provided with sealing means 34, as inFIG. 2, substantially at the lower end of the tubular housing. However,this sealing means may be provided at any point along the tubularhousing and, in FIG. 8, is shown as at 34a substantially intermediatelyalong the housing. The purpose of the seal is to exclude water from theportions of the ramp thereabove so that these portions can be used inmaking up and coating the pipe sections. A string of make-up pipe 35rests on ramp 26 preparatory to emission from the lower end thereofthrough seal 34.

FIG. 7 shows the lower deck structure containing portions 36, 37, and 38constituting work and pipe storage areas and portion 39 foraccommodating the living quarters of the crew. A ballast pump 40 andoperating engine 41 .are shown mounted on deck portion 38, and it will`be understood that suitable piping Will be provided for pumping waterballast both into and out of hollow framing members 9, 10, 17, 18, 19,and 20 for adjusting the draft of the apparatus, as will be explained.Also mounted on the deck structure a-re rotating cranes 4Z (FIG. 3) andother pipe-handling equipment for transferring pipe sections from thestorage areas to the pipe make-up regions at the upper end 27 of theramp. As will be well-understood, suitable space and equipment will beprovided along the ramp for connecting the pipe sections serially to thepipe st-ring on the ramp and suitably coating and otherwise treating thepipe.

In use, the apparatus, with the ballast tanks evacuated to provide asufficiently shallow draft, will be towed to the scene of operations.While the proportions and size of the apparatus will depend uopn thedepth of water in which it is intended to be used and thecharacteristics of the pipe it is to lay, exemplary di-mensions are onthe order of 600 foot length and 200 foot overall height. This apparatuswill operate in water of approximately 24U-foot depth and with theballast tanks filled will submerge until its bottom is approximately 40feet from the water bottom and with the upper 40 feet of the structureprojecting above the surface of the water as stabilizing freeboard. Withthe living and work quarters occupying the rear 20() feet of the vessel,the forward 400 feet would be, in effect, ramp support structure, thoughrigid with the remainder of the vessel. With the vessel so dimensioned,the ramp would be inclined at approximately 26 degrees from horizontal.

Wit-h reference to diagrammatic FIG. 8, there is shown a buoyant,skeletonized structure having an overall length of 600 feet and heightof about 200 feet. This would provide for a ramp angle if approximately26 degrees and a length of unsupported pipe between the end of the bargeF and the water bottom at E f somewhat more than 200 feet. The sharpnessof the curve at point E is affected both by the height of the pipe feedopening 33 at the bottom of the semi-submersible structure above thewater bottom and the length of the structure. A smaller angle of rampinclination may be necessary where very large and relatively stiff pipeis being laid.

In order to maintain only a safe length of the pipe unsupported as thewater depth varies, it may be necessary to vary the draft `of thestructure by adjusting the water ballast in the ballast tanks. Thus, thevessel may be utilized in a rather wide range of water depths. Also,where the pipe is to be laid in shallower water, the height and lengthof the vessel may be reduced.

It is desirable, of course, to make up as large a pipe string on theramp as possible before moving the laying structure forwardly so as todischarge the pipe from the rear end thereof. The position of seal orwater lock 34 or 34a will be adjusted to provide for the proper pipemakeup and pipe-treating area and this area, of course, may extendsubstantially below the surface of the water. Finally, in case the crewmust leave the vessel, it is only necessary to fill the ballast tanks soas to drop the vessel to the bottom in which position it will ride outany storm without disconnection of the pipe string therefrom. When thecrew returns, the ballast tanks are evacuated sufficiently to againelevate the vessel to the desired operating position. However, due to-t'he skeletonized lconstruction and the low center -of gravity, thevessel will be exceptionally stable, even in very rough water, so t-hatwork may continue even when other types of vessels would have to leavethe scene.

The invention may be modified in various respects as will occur to thoseskilled in the art, .and the exclusive use of all modifications as comewithin the scope :of the appended claims is contemplated.

I claim:

1. Apparatus for laying submerged pipe comprising an elongated, buoyanthull structure having a lower, normally submerged pipe delivery opening`at one end, fa pipe conveyor ramp rigidly mounted on said hullstructure in a fixed, central position thereof and extending from saidopening upwardly at an angle lengthwise of said structure, pipe linemake-up and coating Imeans on the upper part of said ramp, `an enclosurefor a part of said ramp, sealing Imeans in said enclosure for excludingwater from at least said upper part of said ramA means for adjusting thewater ballast in said hull structure to control the draft thereof, andmeans for transferring pipe sections to said ramp upper part forconnection to a pipe string on said ramp.

2. Pipe-laying apparatus as described in claim 1 further includingstorage and working quarters on the upper par-t of said hull structure.

3. Apparatus for laying submerged pipe comprising a rigid framework ofat least partially hollow members forming an elongated, skeletonized,buoyant hull structure, a pipe conveyor ramp rigidly mounted on saidhull structure in a fixed, central position thereof and extending fromone submerged end of said structure at the `bottom longitudinally andupwardly at an angle therethrough to an adjacent upper freeboard part ofthe structure, deck means on the upper part of said hull structure,storage` and working quarters on said deck means, means for transferringpipe sections to t-he upper part of said ramp for connection to a pipestring thereon, and means for adjusting the ballast in said hollowmembers to control the draft of said structure and, thereby, the lengthand curvature of pipe between the lower end of said ramp .and theunderlying water bottom.

4. Apparatus for laying submerged pipe, as described in claim 3, furtherincluding enclosure -rneans for at least a portion of said ramp, andmeans sealing said enclosure means against entry of water into saidportion whereby said portion may be utilized for makeup and coating ofpipe on said ramp.

References Cited UNITED STATES PATENTS 1,152,326 8/1915 Lewis 61-72.42,910,835 11/1959 Timothy 61 72.3 3,082,608 3/1963 Danieli 6l-46.53,104,531 9/1963 McCammon 61-46.5 3,136,133 6/1964 Perret 61-7233,214,921 1l/1965 Goepfert et al. 61-72.3 3,241,324 3/1966 Storm et al.61-46.5 3,266,256 8/1966 Postlewaite et al. 6l-72.3 3,273,346 9/1966Delaurelle et al 61-72.3 3,280,571 10/1966 Hauber et al. 61-72.1

FOREIGN PATENTS 885,276 12/1961 Great Britain. 947,196- 1/ 1964 GreatBritain.

EARL I.A WITMER, Primary Examiner.

